This invention relates to an obstacle detection system for an autonomous cleaning robot.
There is a long felt need for autonomous robotic cleaning devices for dusting, mopping, vacuuming, and sweeping operations. Although technology exists for complex robots which can, to some extent, xe2x80x9cseexe2x80x9d and xe2x80x9cfeelxe2x80x9d their surroundings, the complexity, expense and power requirements associated with these types of robotic subsystems render them unsuitable for the consumer marketplace.
The assignee of the subject application has devised a less expensive, battery operated, autonomous cleaning robot which operates in two modes: random and wall following. In the random bounce mode, the processing circuitry of the robot causes it to move in a straight line until the robot comes into contact with an obstacle; the robot then turns away from the obstacle and heads in a random direction. In the wall following mode, the robot encounters a wall, follows it for a time, and then returns to the random mode. By using this combination of modes, robotic theory has proven that the floor including the edges thereof is adequately covered in an optimal time resulting in a power savings.
Unfortunately, however, presently available sensor subsystems such as sonar sensors for detecting obstacles on or in the floor or for detecting the wall in order to enter the wall following mode (or to avoid bumping into the wall) are either too complex or too expensive of both. Tactile sensors are inefficient.
It is therefore an object of this invention to provide a robot obstacle detection system which is simple in design, low cost, accurate, easy to implement, and easy to calibrate.
It is a further object of this invention to provide such a robot detection system which prevents an autonomous cleaning robot from driving off a stair or over an obstacle which is too high or too low.
It is a further object of this invention to provide a robotic wall detection system which is low cost, accurate, easy to implement and easy to calibrate.
It is a further object of this invention to provide such a robot wall detection system which effects smoother robot operation in the wall following mode.
It is a further object of this invention to provide a sensor subsystem for a robot which consumes a minimal amount of power.
It is a further object of this invention to provide a sensor subsystem which is unaffected by surfaces of different reflectivity.
The invention results from the realization that a low cost, accurate, and easy to implement system for either preventing an autonomous cleaning robot from driving off a stair or over an obstacle which is too high or too low and/or for more smoothly causing the robot to follow a wall for more thorough cleaning can be effected by intersecting the field of view of a detector with the field of emission of a directed beam at a predetermined region and then detecting whether the floor or wall occupies that region. If the floor does not occupy the predefined region, a stair or some other obstacle is present and the robot is directed away accordingly. If a wall occupies the region, the robot is first turned away from the wall and then turned back towards the wall at decreasing radiuses of curvature until the wall once again occupies the region of intersection to effect smoother robot operation in the wall following mode.
This invention features an autonomous robot comprising a housing which navigates in at least one direction on a surface. A first sensor subsystem is aimed at the surface for detecting obstacles on the surface. A second sensor subsystem is aimed at least proximate the direction of navigation for detecting walls. Each subsystem includes an optical emitter which emits a directed beam having a defined field of emission and a photon detector having a defined field of view which intersects the field of emission of the emitter at a finite, predetermined region.
The robot obstacle detection system of this invention features a robot housing which navigates with respect to a surface and a sensor subsystem having a defined relationship with respect to the housing and aimed at the surface for detecting the surface. The sensor subsystem includes an optical emitter which emits a directed beam having a defined field of emission and a photon detector having a defined field of view which intersects the field of emission of the emitter at a region. A circuit in communication with the detector then redirects the robot when the surface does not occupy the region to avoid obstacles.
Typically, there are a plurality of sensor subsystems spaced from each other on the housing of the robot and the circuit includes logic for detecting whether any detector has failed to detect a beam from an emitter.
In one embodiment, the robot includes a surface cleaning brush. The emitter typically includes an infrared light source and the detector then includes an infrared photon detector. A modulator connected to the infrared light source modulates the directed infrared light source beam at a predetermined frequency and photon detector is tuned to that frequency. The emitter usually includes an emitter collimator about the infrared light source for directing the beam and the detector then further includes a detector collimator about the infrared photon detector. The emitter collimator and the detector collimator are preferably angled with respect to the surface to define a finite region of intersection.
The robot wall detection system of this invention includes a robot housing which navigates with respect to a wall and a sensor subsystem having a defined relationship with respect to the housing and aimed at the wall for detecting the presence of the wall. The sensor subsystem includes an emitter which emits a directed beam having a defined field of emission and a detector having a defined field of view which intersects the field of emission of the emitter at a region. A circuit in communication with the detector redirects the robot when the wall occupies the region.
In the preferred embodiment, there are a plurality of sensor subsystems spaced from each other on the housing of the robot and the circuit includes logic for detecting whether any detector has detected a beam from an emitter.
The circuit includes logic which redirects the robot away from the wall when the wall occupies the region and back towards the wall when the wall no longer occupies the region of intersection preferably at decreasing radiuses of curvature until the wall once again occupies the region of intersection to effect smooth operation of the robot in the wall following mode.
The sensor subsystem for an autonomous robot which rides on a surface in accordance with this invention includes an optical emitter which emits a directed optical beam having a defined field of emission, a photon detector having a defined field of view which intersects the field of emission of the emitter at a region and a circuit in communication with a detector for providing an output when an object is not present in the region.
If the object is the surface, the output from the circuit causes the robot to be directed to avoid an obstacle. If, on the other hand, the object is a wall, the output from the circuit causes the robot to be directed back towards the wall.